linux-kernel - Re: [PATCH] dm crypt: Convert essiv from ahash to shash

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Message-ID: <CAK8P3a10ONoVAt8+5TNaYzM2qaH=0THkx16tZCd7hpcx-TWvBQ@mail.gmail.com>
Date:   Mon, 16 Jul 2018 12:23:56 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Eric Biggers <ebiggers@...gle.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        dm-devel@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dm crypt: Convert essiv from ahash to shash

On Mon, Jul 16, 2018 at 5:59 AM, Kees Cook <keescook@...omium.org> wrote:
> In preparing to remove all stack VLA usage from the kernel[1], this
> removes the discouraged use of AHASH_REQUEST_ON_STACK in favor of
> the smaller SHASH_DESC_ON_STACK by converting from ahash-wrapped-shash
> to direct shash. The stack allocation will be made a fixed size in a
> later patch to the crypto subsystem.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

This looks very nice, it should also make the operation more efficient in the
process by removing one indirection layer.

     Arnd